The present invention relates to ATM transmission, and particularly to a short cell multiplexing for transmitting, over an ATM network, data shorter than the payload of a standard ATM cell (basically less than 48 bytes, but more than 48 bytes can be allowed) which is transmitted through a network such as an ATM network, private short cell network, STM (Synchronous Transport Module) network, radio, packet network, or FR (Frame Relay) network.
Forming ATM cells from low bit rate, highly real time information like voice will cause a large delay time if the information is stored fully in the payload of the standard ATM cell, resulting in the degradation in the information. To prevent this, a partial fill method is proposed which loads the information partially (into part of the ATM cell) to be transmitted.
On the other hand, in a local environment like premises, a short cell using a payload shorter than the 48-byte payload of the standard ATM cell is proposed, which is expected to match better to the low bit rate data.
FIGS. 30A and 30B illustrate the partial fill method and short cell method.
In the partial fill method as shown in FIG. 30A, a partial fill cell assembler 12 forms a standard ATM cell by adding dummy data to input data, and outputs it to a B-ISDN network. A partial fill cell disassembler 13 extracts the data from the partial fill cell received from the B-ISDN network, and outputs it.
In the short cell method as shown in FIG. 30B, a short cell assembler 14 forms from input data a short cell matching to an intended data length, and outputs it to an exclusive network having a unique cell slot structure. A short cell disassembler 15 extracts the data from the short cell received from the exclusive network, and outputs it.
The partial fill method described as the conventional techniques has a problem in that it impairs efficiency of utilizing the payload of the standard ATM cell and hence the transmission efficiency accompanying that because it uses only part of the payload of the standard ATM cell.
The short cell method, on the other hand, requires the exclusive network with a unique cell slot structure, which causes a problem of bad matching with the standard ATM switching network (B-ISDN network).
In view of these, a short cell multiplex transmission method is proposed which multiplexes information from multiple users to a single ATM cell (ISS"" 95 Nakajima). This method multiplexes short packets received from different users within a predetermined time period into the payload of an ATM cell. This has advantages of limiting the delay below a certain fixed amount, thereby improving the efficiency.
In connection with the transmission method, a Shinagawa patent is disclosed. Besides, a Mita patent application has been filed which increases the degree of freedom in combining the users to be multiplexed.
In handling variable length user data, the following two methods can be considered: A first method fills the variable length user data into a predetermined fixed length short cell and fills dummy information into the remainder of the cell; and a second method forms variable length short cells in accordance with the user data, thereby multiplexing/demultiplexing them into or from the ATM cell. Although the second method is superior to the first method in efficiency, it requires a technique to decide the length of the variable short cells which vary for each ATM cell to extract them. The second method has another problem in that its payload efficiency is somewhat impaired as compared with the method which transmits the payload after filling it completely, because the second method, if higher transmission efficiency is required, transmits the ATM payload after loading it with the dummy information when its occupation ratio reaches to a certain level and no new short cell can be expected to be multiplexed into the ATM cell. Thus, a cell overlapping technique is effective which allows a variable length short cell to undergo multiplexing/demultiplexing across more than one ATM cell (Docomo, ATM-F).
In connection with one of the technique of multiplexing/demultiplexing variable short cells into or from one or more ATM cells, ATT filed a letter to ITU. According to the ATT letter, each short cell is provided with length information and user identifier (LLN: logical link number) to implement the extraction of variable length short cells. The first half of a short cell extending over two ATM cells is provided with the length information indicating the entire length of the short cell, and the second half multiplexed at the initial position of the next ATM cell is provided with the length information indicating only the length of the latter part of the short cell. A receiving end, when the length information of the short cell exceeds the end of the payload of the ATM cell, decides that it continues to the next ATM cell, and combines the first half and second half of the short cell overlapping the two ATM cell when the length of the remainder of the short cell equals the length indicated by the length information of the latter half multiplexed into the initial position of the next received ATM cell.
This method, however, has the following two problems if the synchronization for the extraction processing of the short cell is lost owing to the loss of the ATM cell during its transmission. First, if the length information of the second half of the short cell multiplexed into the initial position of the ATM cell received after the cell loss disagrees with the length of the remainder expected from the previously received first half of the overlapping short cell, it is impossible to decide whether or not the short cell multiplexed at the initial position of the next received ATM cell is a complete short cell or the continued short cell from the lost ATM cell, even though the cell loss can be detected (problem 1). Second, in spite of the cell loss, if the expected length of the remainder happens to agree with the length information of the latter half of the short cell multiplexed into the initial position of the ATM cell received after the cell loss, not only the cell loss is undetected, but also erroneous short cells are combined (problem 2).
The present invention features the following three aspects in connection with the variable short cell multiplexed transmission system and method.
(1) A multiplex transmission method providing each short cell with information for multiplexing and demultiplexing (embodiment 1).
(2) A multiplex transmission method providing each ATM cell collectively with information for multiplexing and demultiplexing (embodiment 2).
(3) A multiplex transmission method providing no information for multiplexing and demultiplexing (embodiment 3).
Although the item (1) has a similar characteristic to that of the ATT letter in that multiplexing and demultiplexing is carried out by providing each short cell with the length information, it solves the problem 1 of the ATT letter by deciding the cell overlapping not by the length information but by proving short cell status information. Furthermore, it can add control information on the ATM transmission to the multiplexed data of the short cells to achieve more reliable detection of the cell loss for each ATM cell as an option to solve the problem 2.
The foregoing items (2) and (3) relate to novel short cell multiplex transmission methods which have not yet been disclosed.
According to the first aspect of the present invention, a short cell multiplexing ATM transmission system comprises:
a standard ATM cell assembler (1) for forming short cells from various types of input information, and for multiplexing the short cells to be placed in a payload of one or more standard ATM cells to be output to an ATM switching network;
an ATM switching network (7) for transmitting the standard ATM cells; and
a standard ATM cell disassembler (2) for receiving a short cell multiplexed ATM cell, and for disassembling the short cell multiplexed ATM cell into short cells which are converted into an output data format of a channel and output to the channel.
According to the second aspect of the present invention, a standard ATM cell assembler comprises:
a data receiver/short cell assembler (3) for receiving various types of input information such as private short cells, ATM cells, STM frames, information packets of a frame relay or a packet network, TDMA/FDMA radio frames, and CDMA radio packets, and for forming short cells for each type of the information;
a short cell multiplexer (4) for multiplexing short cells onto a payload of one or more standard ATM cells;
a standard ATM cell generator (5) for receiving multiplexed data as a standard ATM payload, and for forming a standard ATM cell by adding an AAL and a header; and
an ATM cell transmitter (6) for outputting the standard ATM cell to an ATM switching network.
In the standard ATM cell assembler (1), the standard ATM cell generator (5) may form the standard ATM cell by inputting data other than the multiplexed data fed from the short cell multiplexer (4).
In the standard ATM cell assembler (1), the data receiver/short cell assembler (3) may comprise:
a data receiving portion (3-1) for receiving various types of data such as private short cells, ATM cells, STM frames, information packets of a frame relay or a packet network, TDMA/FDMA radio frames, and CDMA radio packets;
an SC-PL assembler (3-2) for forming a payload of a short cell (SC-PL) by extracting input data frame by frame or packet by packet;
an SC-AAL provider (3-3) for providing an AAL of the short cell based on attributes of the data as needed; and
an SC-H provider (3-4) for providing a header of the short cell by converting address information of the data.
In the standard ATM cell assembler (1), the short cell multiplexer (4) may comprise:
a multiplexing combination determiner A (4A-1) for deciding a combination and order of multiplexing parties of a plurality of input short cells with a free length in accordance with purposes (such as multiplexing data for each data attribute, for each identical cell length, for each identical route);
a short cell information provider A (4A-2) for providing each short cell with short cell information including length information of the short cell; and
a short cell multiplexing portion A (4A-3) for linking the short cells provided with the short cell information in accordance with a decision of the multiplexing combination determiner A (4A-1).
In the standard ATM cell assembler (1), the short cell multiplexer (4) may comprise:
a multiplexing combination determiner B (4B-1) for deciding a combination and order from among predetermined multiplexing parties of a plurality of input short cells with a free length in accordance with purposes (such as multiplexing data for each data attribute, for each identical cell length, for each identical route);
a multiplexing information generator B (4B-2) for generating multiplexing information including information on lengths and a number of short cells to be multiplexed; and
a short cell multiplexing portion B (4B-3) for linking the short cells and the multiplexing information in accordance with a decision of the multiplexing combination determiner B (4B-1).
In the standard ATM cell assembler (1), the short cell multiplexer (4) may comprise:
a multiplexing combination determiner C (4C-1) for deciding a combination and order from among predetermined multiplexing parties of a plurality of input short cells with a free length in accordance with purposes (such as multiplexing data for each data attribute, for each identical cell length, for each identical route); and
a short cell multiplexing portion C (4C-2) for linking the short cells in accordance with a decision of the multiplexing combination determiner C (4C-1).
In the standard ATM cell assembler (1), the multiplexing information may include multiplex pattern identifiers (PI) representing a multiplexed data structure to make correspondence between the multiplex pattern identifiers and the multiplexed data structures, and wherein the short cell multiplexer (4) provides multiplexing information corresponding to the multiplexed data structure.
In the standard ATM cell assembler (1), the multiplexing information may include:
multiplexed cell number information (N) indicating a number of identical length short cells multiplexed onto a payload of a standard ATM cell; and
short cell length information (L) indicating a length of multiplexed short cells, and
wherein the short cell multiplexer (4) provides multiplexing information corresponding to a multiplexed data structure.
In the standard ATM cell assembler (1), the multiplexing information may include:
multiplexed cell number information (N) indicating a number of short cells multiplexed onto a payload of a standard ATM cell, and short cell length information (LI1-LIN) indicating a length of each of the multiplexed short cells, and
wherein the short cell multiplexer (4) provides multiplexing information corresponding to a multiplexed data structure.
According to the third aspect of the present invention, a standard ATM cell disassembler comprises:
an ATM cell receiver (8) for receiving standard ATM cells sent from a B-ISDN network (7);
a standard ATM cell processor (9) for obtaining payloads by carrying out disassembly/processing of the received standard ATM cells;
a short cell disassembler (10) for disassembling obtained payloads into short cells; and
a short cell processor/data transmitter (11) for carrying out a predetermined processing of each of the short cells to convert them into various types of output information such as private short cells, ATM cells, STM cells, information packets of a frame relay or a packet network, TDMA/FDMA radio frames, and CDMA radio packets, and for outputting the converted data to respective channels.
In the standard ATM cell disassembler (2), the standard ATM cell processor (9) may output data other than to the short cell disassembler (10) to have the ATM standard cells processed.
In the standard ATM cell disassembler (2), the short cell disassembler (10) may extract short cell information sequentially beginning from an initial position of multiplexed data, and disassembles the multiplexed data into short cells by analyzing the short cell information.
In the standard ATM cell disassembler (2), the short cell disassembler (10) may comprise:
a multiplexing information analyzer B (10B-1) for extracting and analyzing multiplexing information; and
a short cell disassembler B (10B-2) for disassembling multiplexed data into short cells in accordance with analyzed results given by the multiplexing information analyzer B (10B-1).
In the standard ATM cell disassembler (2), the short cell disassembler (10) may disassemble multiplexed data into short cells in accordance with a predetermined structure.
In the standard ATM cell disassembler (2), the short cell processor/data transmitter (11) may comprise:
an SC-H processor (11-1) for processing a of a received short cell SC-H;
an SC-AAL processor (11-2) for carrying out an AAL processing if the short cell includes an AAL;
an SC-PL processor (11-3) for processing a payload of the short cell; and
a data transmitter (11-4) for converting the short cell to each format of output data to be output to a channel.
In the standard ATM cell disassembler (2), the multiplexing information of the standard ATM cell may include multiplex pattern identifiers (PI) representing a multiplexed data structure to make correspondence between the multiplex pattern identifiers and the multiplexed data structures, and wherein the short cell disassembler (10) disassembles into the multiplexed data structure corresponding to the multiplexing information.
In the standard ATM cell disassembler (2), the multiplexing information of the standard ATM cell may include:
multiplexed cell number information (N) indicating a number of identical length short cells multiplexed onto a payload of the standard ATM cell; and
short cell length information (L) indicating a length of the multiplexed short cells, and
wherein the short cell disassembler (10) disassembles into a multiplexed data structure corresponding to the multiplexing information.
In the standard ATM cell disassembler (2), the multiplexing information may include:
multiplexed cell number information (N) indicating a number of short cells multiplexed onto a payload of a standard ATM cell, and short cell length information (LI1-LIN) indicating a length of each of the multiplexed short cells, and
wherein the short cell disassembler (10) disassembles into a multiplexed data structure corresponding to the multiplexing information.
Here, the standard ATM cell assembler/disassembler may comprise the standard ATM cell assembler (1) and the standard ATM cell disassembler (2).
In the standard ATM cell assembler/disassembler, the short cell hierarchically may multiplex sub-short cells.
According to the fourth aspect of the present invention, a short cell multiplexing ATM transmission method comprises the steps of:
assembling one or more standard ATM cells to be output to an ATM switching network, each the standard ATM cell including a payload including one or more multiplexed short cells formed from various types of input information;
transmitting the standard ATM cells; and
receiving short cell multiplexed ATM cells, disassembles them into short cells, and output them to a channel after converting into an output data format.
In the short cell multiplexing ATM transmission method, the short cell may hierarchically multiplex sub-short cells.
According to the fifth aspect of the present invention, a short cell multiplexing ATM transmission method comprises the steps of:
forming short cells from various types of input information, multiplexing the short cells to be placed in a payload of one or more standard ATM cells, receiving multiplexed data as a standard ATM payload, assembling a standard ATM cell by adding an AAL and a header to be sent to an ATM switching network;
receiving a short cell multiplexed ATM cell, disassembling the received short cell multiplexed ATM cell to obtain its payload, disassembles the obtained payload into short cells which are converted into an output data format to be output to a channel.
According to the sixth aspect of the present invention, a short cell multiplexing ATM transmission method comprising the steps of:
forming short cells from various types of input information, providing each short cell with information which must be individually provided for the short cells as a short cell multiplexing individual AAL, forming multiplexed data by multiplexing the short cells, providing the multiplexed data with a short cell multiplexing common AAL shared by ATM cells assembled, providing the standard ATM cells with an ATM header and sends the standard ATM cells to an ATM switching network;
receiving the short cell multiplexed ATM cells, and routing them to processors in accordance with the ATM headers;
extracting short cells through processing of the multiplexed data in accordance with a combination of the short cell multiplexing common AAL and the short cell multiplexing individual AAL; and
individually processing the short cells in accordance with the short cell multiplexing individual AAL, and converting the short cells into output data to be output.
In the short cell multiplexing ATM transmission method, the combination of the short cell multiplexing common AAL and the short cell multiplexing individual AAL may comprise, in the short cell multiplexing individual AAL, length information and overlapping information.
In the short cell multiplexing ATM transmission method, the combination of the short cell multiplexing common AAL and the short cell multiplexing individual AAL may comprise, in the short cell multiplexing common AAL, length information and overlapping information.
In the short cell multiplexing ATM transmission method, the combination of the short cell multiplexing common AAL and the short cell multiplexing individual AAL may comprise overlapping information in the short cell multiplexing common AAL, and length information in the short cell multiplexing individual AAL.
According to the seventh aspect of the present invention, a standard ATM cell assembler which receives various types of input information such as private short cells, ATM, STM frames, information packets of a frame relay or a packet network, TDMA/FDMA radio frames, and CDMA radio packets, and assembles standard ATM cells, the standard ATM cell assembler comprises:
means for providing an AAL common to the assembled standard ATM cell as a short cell multiplexing common AAL; and
means for providing information which must be individually provided for the short cells as a short cell multiplexing individual AAL.
In the standard ATM cell assembler, the short cell multiplexing individual AAL may be provided with length information for short cell multiplexing.
In the standard ATM cell assembler, the length information may provide a length of a short cell to be multiplexed before dividing the short cell.
In the standard ATM cell assembler, the length information may provide a length of a short cell divided into units each corresponding to the standard ATM cell.
In the standard ATM cell assembler, the short cell multiplexing common AAL may be provided with length information for short cell multiplexing.
In the standard ATM cell assembler, the short cell multiplexing common AAL may be provided with overlapping information indicating that the short cell is multiplexed onto standard ATM cells in an overlapped manner.
In the standard ATM cell assembler, the short cell multiplexing individual AAL may be provided with overlapping information indicating that the short cell is multiplexed onto standard ATM cells in an overlapped manner.
In the standard ATM cell assembler, the short cell multiplexing individual AAL may be provided with information for individually processing the short cells.
In the standard ATM cell assembler, the information for individually processing the short cells may be provided with information identifying switched points of speech burst/mute.
In the standard ATM cell assembler, the information for individually processing the short cells may be provided with information indicating individuality of contents of data included in the short cells, or with information indicating quality.
According to the eighth aspect of the present invention, a standard ATM cell assembler comprises providing a short cell multiplexing individual AAL which is provided with length information after division.
According to the ninth aspect of the present invention, a standard ATM cell disassembler which receives standard ATM cells assembled from various types of input data such as private short cells, ATM, STM frames, information packets of a frame relay or a packet network, TDMA/FDMA radio frames, and CDMA radio packets, and disassembles the standard ATM cells into short cells, the standard ATM cell disassembler comprises:
means for disassembling into short cells using a short cell multiplexing common AAL which is provided in common to the standard ATM cells and a short cell multiplexing individual AAL which is provided individually for the short cells; and
means for carrying out processing of disassembled individual short cells.
In the standard ATM cell disassembler, the short cell multiplexing individual AAL may be provided with length information for short cell multiplexing.
In the standard ATM cell disassembler, the length information may be provided with a length of the multiplexed short cells before division.
In the standard ATM cell disassembler, the length information may be provided with lengths after divided into units each corresponding to the standard ATM cell.
According to the tenth aspect of the present invention, a standard ATM cell disassembler comprises providing a short cell multiplexing individual AAL which is provided with length information after division.
In the standard ATM cell disassembler, the short cell multiplexing common AAL may be provided with length information for short cell multiplexing.
In the standard ATM cell disassembler, the short cell multiplexing common AAL may be provided with overlapping information indicating that the short cell is multiplexed onto standard ATM cells in an overlapped manner.
In the standard ATM cell disassembler, the short cell multiplexing individual AAL may be provided with overlapping information indicating that the short cell is multiplexed onto standard ATM cells in an overlapped manner.
In the standard ATM cell disassembler, the short cell multiplexing individual AAL may be provided with information for individually processing the short cells.
In the standard ATM cell disassembler, the information for individually processing the short cells may be provided with information identifying switched points of speech burst/mute.
In the standard ATM cell disassembler, the information for individually processing the short cells may be provided with information indicating individuality of contents of data included in the short cells, or with information indicating quality.
Here, the short cell multiplexing ATM transmission system, in which a standard ATM cell assembler may be linked with a standard ATM cell disassembler via a standard ATM cell switching network.
In the short cell multiplexing ATM transmission system, the short cell may hierarchically multiplex sub-short cells.
In the SC-AAL provider (3-3, 3-3xe2x80x2) of a data receiver/short cell assembler (3) in the standard ATM cell assembler (1), the SC-AAL provider may provide a last one or a first one of divided user data with a final identifier or an initial identifier as the SC-AAL.
In the SC-AAL provider of a data receiver/short cell assembler (3), the final identifier may comprise an identifying bit indicating that the divided user data is the last one.
In the SC-AAL provider of a data receiver/short cell assembler (3), the initial identifier may comprise an identifying bit indicating that the divided user data is the first one.